In the prior art, there are wiring substrates for mounting semiconductor chips, or the like. As such a wiring substrate, a technique which uses a porous aluminum oxide substrate having many penetration conductors penetrating in the thickness direction, has been developed.
According to this technique, a wiring substrate that enables electric conduction between an upper side and a lower side is constructed on the basis of forming wirings on both faces of the aluminum oxide substrate in which the penetration conductors are formed, the wirings being connected to selected plural penetration conductors.
A related art is disclosed in Japanese Laid-open Patent Publication No. 2004-273480, and Japanese Laid-open Patent Publication No. 2009-147241.